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UNIT I FUNDAMENTALS OF ANALOG COMMUNICATION Principles of amplitude modulation, AM envelope, frequency spectrum and bandwidth, modulationindex and percent modulation, AM Voltage distribution, AM power distribution, Angle modulation - FM and PM waveforms, phase deviation and modulation index, frequencydeviation and percent modulation, Frequency analysis of angle modulated waves. Bandwidth requirementsfor Angle modulated waves. 1. Principles of amplitude modulation 1) Define modulation. 2) Define demodulation. 3) What is the need for modulation? 4) Define Amplitude modulation. 5) Give the explanation for AM envelope. 6) Illustrate the relationship among carrier, modulating and modulated signals using a neat diagram. 7) What is modulation index and percentage modulation in AM? 8) Explain in detail about Frequency spectrum of AM. 9) How will you calculate bandwidth from the given frequency spectrum. 2. Coefficient of Modulation and percent modulation 1) Define Coefficient of Modulation 2) Define percent modulation 3) Give the equations for Coefficient of Modulation and percent modulation and explain the terms 4) Give the formulae to calculate the peak amplitudes of upper and lower side frequencies 5) Write the equation for percent modulation in terms of Vmax and Vmin 3. AM Voltage distribution and AM power distribution 1) Give the expression for unmodulated carrier and amplitude modulated wave. 2) Write the expression for modulated signal in terms of using carrier, upper and lower side signals. 3) Write the formulas to find upper and lower side frequencies by using the carrier and message frequencies. 4) What is the expression for power in an unmodulated carrier? 5) Express the power of side bands in terms of peak power voltage and load resistance. 6) Write the expression for total power in an AM DSBFC envelope. 7) What will be the transmitted power in case of m=0? 8) How the total power is varied according to the modulation index. 9) Explain about the power in case of 100% modulation. 10) Write the expression for the total power of side bands. 4. Angle modulation 1) What are the forms of angle modulation? 2) What are the limitations (or) disadvantages of angles modulation? 3) What are the advantages of angles modulation? 4) Write the mathematical expression of angle modulated wave and explain the notations. 5) Define Direct frequency modulation. 6) Define Direct phase modulation. 7) Give explanation about phase deviation. 8) Give explanation about frequency deviation. 9) What is meant by Carrier rests frequency. 10) Define instantaneous phase deviation. 11) Define instantaneous phase. 12) Define instantaneous frequency deviation. 13) Define instantaneous frequency. 14) Explain about the deviation sensitivity of PM and FM and give the expressions. 5. FM and PM waveforms 1) Draw the wave form of FM and give the explanation. 2) Draw the wave form of PM and give the explanation. PREPARED BY: PARTHIBAN. S., ASST. PROF., VRS COLLEGE OF ENGG. AND TECHNOLOGY, VILLUPURAM

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3) Explain the frequency deviation characteristics in FM. 4) Explain the frequency deviation characteristics in PM. 5) Explain FM in terms of instantaneous frequency. 6) Explain PM in terms of instantaneous phase. 6. Phase deviation and modulation index 1) Write the general equation of angle modulation in terms of modulation index. 2) What is meant by peak phase deviation? 3) What is modulation index in PM? 4) What is meant by index of modulation? 5) Give the expression and derive the unit for modulation index of PM. 6) Give the expression and derive the unit for modulation index of FM. 7. Frequency deviation and percent modulation 1) Define frequency deviation. 2) Define carrier swing. 3) Write the equation for frequency deviation. 4) Write the three forms equation for FM in terms of K1, ∆f and m. 5) Express modulation index in terms of frequency deviation and modulating signal frequency. 6) How the PM and FM modulation indexes varies with modulating signal frequency? 7) How the percent modulation is calculated in angle modulation? 8. Frequency analysis of angle modulated waves 1) Frequency analysis of Angle modulation is complex, why? 2) How the side frequencies are related to the carrier frequency through modulating signal frequency? 3) Write one of the Bessel function identity used for angle modulation. 4) Express the angle modulation general equation in terms of Bessel function. 5) Write the first four terms of Bessel series. 6) Write the Bessel sets of frequency components resulted in angle modulation. 7) Write the Jn(m) equation to solve the amplitude of the side frequencies. 8) What if meant by first carrier null? 9) What if meant by second carrier null? 9. Bandwidth requirements for Angle modulated waves 1) Write the classification of angle modulated waveforms in terms in terms of indexes. 2) What is meant by narrowband FM? 3) What is quasi stationary approach? 4) How the low index modulation is related to amplitude modulation? 5) How will you calculate the minimum bandwidth from Bessel table? 6) Write Carson’s rule for bandwidth 7) Which one is accurate to calculate bandwidth among Bessel and Cason’s rules? Justify your answer.Frequently asked questions… (Slanting style – Most important) 1. Distinguish between FM and PM by giving its mathematical analysis. (8m) 2. Discuss about the sets of side bands produced when a carrier is frequency modulated by a single frequency sinusoid. (8m) 3. Explain the principles of amplitude modulation. (8m) 4. AM: Voltage distribution and power distribution 5. In an AM modulator, 500 KHz carrier of amplitude 20 V is modulated by 10 KHz modulating signal which causes a change in the output wave of +_ 7.5 V. Determine: (1) Upper and lower side band frequencies (2) Modulation Index (3) Peak amplitude of upper and lower side frequency (4) Maximum and minimum amplitudes of envelope. (8m) 6. Write a note on frequency spectrum analysis of angle modulated waves. (8m) 7. Derive the relationship between the voltage amplitudes of the side band frequencies and the carrier and draw the frequency spectrum. (8m) 8. Explain the band width requirements of angle modulated waves. (8m) PREPARED BY: PARTHIBAN. S., ASST. PROF., VRS COLLEGE OF ENGG. AND TECHNOLOGY, VILLUPURAM

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8. Phase shift keying 1) Define PSK. 2) Differentiate PSK and Conventional phase modulation. 9. Binary phase shift keying 1) Define BPSK 2) What are the other names of BPSK (Phase Reversal Keying or Biphase modulation) BPSK transmitter 3) Draw the block diagram of BPSK transmitter. 4) What is the function of balanced modulator / Product modulator at transmitter? 5) What is the condition for balanced modulator to operate properly? (Digital I/p V > peak carrier voltage) 6) Write about the switching elements (Diodes) present in the transmitter during the binary input 1 (or 0)? 7) What is meant by Constellation diagram? (or) What is the difference between phasor diagram and Constellation diagram? 8) Write the truth table of BPSK. 9) Draw the Constellation diagram of BPSK. 10) Draw the phasor diagram of BPSK Bandwidth considerations of BPSK 11) Derive the expression for Bandwidth of BPSK. M-ary Encoding 12) What is M-ary / Beyond binary/ Higher than binary encoding BPSK Receiver 13) Draw the block diagram of BPSK receiver. 14) What is the function of balanced modulator / Product modulator at receiver? 15) What are the input signals of BPSK Receiver? 16) What is the function of LPF in receiver? 17) Derive the reproduction of Logic 1 (or 0) from +sin ωct ( or –sin ωct)10. QPSK 1) Define QPSK 2) What are the other names of QPSK 3) Relate QPSK with M-ary. (M=4), Explain the term Quarternary. 4) What is the function of balanced modulator / Product modulator at transmitter? 5) Explain about the number of Input conditions and Output phases. 6) Explain about Dibits. 7) What is the relationship between input bit rate and output baud rate. (output baud rate = 1/2 input bit rate)? QPSK transmitter 8) Draw the block diagram of QPSK transmitter. 9) Write about Bit splitter. 10) Write about I and Q channels? 11) What are the output signals of QPSK transmitter? (2 logics and 2 phase So 4 O/p’s, Write equations) 12) What is the function of balanced modulator at transmitter? 13) Write the truth table of QPSK. 14) Draw the Constellation diagram of QPSK. 15) Draw the Phasor diagram of QPSK. Bandwidth considerations of QPSK 16) Derive the expression for Bandwidth of QPSK. BPSK Receiver 17) Draw the block diagram of QPSK receiver. 18) What is the function of balanced modulator / Product modulator at receiver? 19) What are the input signals of QPSK Receiver? 20) What is the function of carrier recovery circuit? (i/p and o/p signals) 21) What is the function of Product detector at receiver? 22) What is the function of LPF in receiver? 23) Derive the reproduction of Logic 1 and 0 from -sin ωct + cos ωct. 24) What is offset QPSK? • Similar questions for 8-PSK (Extra: 2-to-4 convertor) and 16-PSK (Extra: Quad bits)PREPARED BY: PARTHIBAN. S., ASST. PROF., VRS COLLEGE OF ENGG. AND TECHNOLOGY, VILLUPURAM

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UNIT III DIGITAL TRANSMISSION Introduction, Pulse modulation, PCM – PCM sampling, sampling rate, signal to quantization noiserate, companding – analog and digital – percentage error, Delta modulation, adaptive delta modulation, differential pulse code modulation, pulse transmission –Intersymbol interference, eye patterns. 1. Introduction 1) What are the advantages of Digital Transmission? 2) What are the disadvantages of Digital Transmission 2. Pulse modulation 1) Define Pulse modulation. 2) What are the four predominant methods of Pulse modulation? 3) Define PWM. 4) Define PPM. 5) Define PAM. (Intermediate form of modulation with PSK, QAM and PCM) 6) Define PCM. 7) Draw the waveforms of PWM, PPM, PAM and PCM. 8) Applications of PWM, PPM, PAM and PCM. 3. PCM 1) Define PCM / PCM Codec. 2) Draw the block diagram a Simple (One-way Only) PCM system. 3) What is the function of Sample and Hold Circuit? 4) What is the function of ADC (Analog to Digital Converter)? 5) What is the function of Parallel to Serial Converter? 6) What is the function of Regenerative repeater? 7) What is the function of Serial to Parallel Converter? 8) What is the function of DAC (Digital to Analog Converter)? 4. PCM sampling 1) What is the need for sampling? (Analog i/p Samples Series of pulses Digital Binary PCM Code) 2) How the Sample and hold circuit helps for the accurate function of ADC? 3) What are the types of sampling? 4) What is meant by Natural sampling? 5) What is meant by Flat top sampling? 6) Differentiate Natural sampling and Flat top sampling 7) Which sampling method is being preferred mostly? Why? 8) What is meant by Aperture error? (Caused by Flat top sampling) 9) What is the function of FET in S&H Circuit? 10) What is the function of Q1 and C1 in S&H Circuit? (or) What are the Sample and Hold Copmonents? 11) Explain Aperture (or) Acquisition time. 12) Define Storage time. 13) What is meant by Aperture Distortion? 14) Write about the Z1 and Z2 in S&H Circuit. 15) Write the combination of components acting as Capacitive voltage-divider network. (FET series with C1: if FET is OFF) 5. Sampling rate 1) State Nyquist Sampling theorem. 2) Write the mathematical expression for Minimum sampling rate (fs). 3) What is meant by Heterodyning or Non linear mixing? 4) Draw and explain the Frequency domain representation of output spectrum from S&H Circuit. 5) What do you meant by Aliasing Effect (or) Fold-over distortion? How it can be removed?(Using Anti aliasing filters or Anti fold-over filter) PREPARED BY: PARTHIBAN. S., ASST. PROF., VRS COLLEGE OF ENGG. AND TECHNOLOGY, VILLUPURAM